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MDO's skin is tougher (impregnated resin), and it paints very well. MDF paints well too. I would favor MDO in a structural situation over MDF, unless the only forces were downward (as in crushing) and the MDF were on edge (like a vertical partition). If MDF gets wet, it's trash. If MDO gets wet, so what - it was made for outdoors (medium density outdoors).

MDF was originally used as substrate material for countertops where the surface would be fully laminated and supported structurally. It runs about 90 lbs. per 4/8 sheet. The high weight tends to make it sag in spans of more than 16-24" unless its supported.

MDO [medium density overlay] is a plywood product with the outer layers made from MDF material. It's designed to give the high structural integrity, reduced weight, and superior screw-holding ability of a plywood product but with the excellent surface paintability of MDF. Like regular ply, it comes in interior and exterior grades.

If you're making cabinets for paint application, the smooth fiber surface on either product is a plus, but, say you wish to make raised panels, the solid MDF would work better for the door panels because you'd have no laminations showing.

Note that any MDF edge to be painted will need to be "sized" or sealed as the stuff soaks up finish like a sponge. Best way, is to use "glue seize" which is a specific product made under several names and should be available at any paint store. I have also used watered down TiteBond (I or II) and it has done well under lacquer. Shellac will work as a sealer also, but it absorbs too much and then takes too long to outgas the solvent.

Note also that carbide tools are called for. MDF is very abrasive and will take the edge of steel cutters (saws, rounters, and jointers) very quickly. Have your dust collector is good shape and dust mask handy, MDF powders when cut or milled. You don't want to route the stuff indoors if you can help it.

Some good comments here. I looked at using MDO for some shop cabinets awhile back, but ended up using birch plywood instead. The only reason was cost...MDO was about 50% more from my suppliers.

Our friend Norm Abram has used a bit of MDO plywood in the last few years for shop cabinetry and some other projects in the New Yankee Workshop. It really does look nice in those applications, even unpainted.

MDO [medium density overlay] is a plywood product with the outer layers made from MDF material.

Mark

Mark, I think you will find that MDO is a plywood product that has a resin impregnated paper coating on one or both sides. The coating is designed to take paint very well. The original use of MDO was--and still is--for highway signage. It's basicly an exterior multyply plywood. I could be wrong, but I've never seen an interior version.

I believe there is a product made as you describe but I don't know what it is called.

Norm uses MDO and now it's vogue....

....for shop cabinets MDO is used for highway signs. Comes in various thickness and sizes. For interior cabinets I wouldn't give it a second thought. Years ago I painted that stuff and was very dissapointed. You could see the "footballs" used to fill the voids. Heaven forbid you use a gloss on it. As noted, MDF aint in the same catagory. I'll stick with plywood for cabinets. MHO

Phil in Big D
The only difference between a taxidermist and the taxman, is that the taxidermist leaves the skin. Mark Twain

I have used MDF for all my shop cabinets. The stuff is strong, albeit heavy, and easy to paint. To preclude a water problem, I attached 1: diameter mail type plastic skids. This raises the cabinet about 1/4" off the floor (concrete). If there is enough water to raise the level of a 20'x20' to 1/4" I'm in deep ca ca. Means my sump pump and/or my generator has quit so I have bigger problems than my cabinets Here's a pic of the last cabinet I made for my drill press.